How Computers Know What We Want — Before We Do

Here's an experiment: try thinking of a song not as a song but as a collection of distinct musical attributes. Maybe the song has political lyrics. That would be an attribute. Maybe it has a police siren in it, or a prominent banjo part, or paired vocal harmony, or punk roots. Any one of those would be an attribute. A song can have as many as 400 attributes — those are just a few of the ones filed under p.

This curious idea originated with Tim Westergren, one of the founders of an Internet radio service based in Oakland, Calif., called Pandora. Every time a new song comes out, someone on Pandora's staff — a specially trained musician or musicologist — goes through a list of possible attributes and assigns the song a numerical rating for each one. Analyzing a song takes about 20 minutes.